This invention relates to an engine starter and more particularly to an engine starter for starting a vehicular engine.
FIG. 1 illustrates one example of a conventional vehicular engine starter in cross section. The engine starter comprises a housing 1 having an opening 2 in which a bearing 3 is inserted The bearing 3 rotatably supports a pinion shifter assembly 4 having a cylindrical shifter main body 4b and a pinion 4a integrally formed on the front end (right end as viewed in FIG. 1) of the shifter main body 4b. The shifter main body 4b also has integrally formed at its rear end (left end as viewed in FIG. 1) a clutch inner member 8b of an over-running clutch 8 which will be explained in more detail later. The engine starter also comprises an electric motor 5 (of which armature shaft only is illustrated) having an output rotary shaft 7 connected to the armature shaft 5 through a planetary speed reduction gear 6 and mounted within the housing 1. The planetary speed reduction gear 6 comprises a sun gear 5a formed on the armature shaft 5 of the electric motor, a plurality of planetary gears 6a rotatably disposed around the sungear 5a by pins on a carrier 6b which integrally extends from the rear end of the output rotary shaft 7, and a stationary inner gear 6c disposed around the planetary gears 6a. The rotary output shaft 7 has helical splines 7a with which inner teeth of a clutch outer member 8a of the over-running clutch 8 engage. A plurality of rollers 8c are disposed between the clutch outer member 8a and the clutch inner member 8b which is an integral extension of the pinion shifter assembly 4. Thus, the clutch outer and inner members 8a and 8b and the rollers 8c together constitute the over-running clutch 8 axially slidably mounted on the output rotary shaft 7. In order to shift the over-running clutch 8 over the output rotary shaft 7, a solenoid switch 9 connected to the over-running clutch 8 by a shift lever 10 is mounted. It is seen that the output rotary shaft 7 is supported by a bearing 12 so that it is rotatable and axially slidable relative to the output rotary shaft 7 within the pinion shifter assembly 4 The output rotary shaft 7 is provided with a stopper ring 13 at the front end of the output rotary shaft 7. Reference numeral 11 designates a spring retainer ring, which also accommodates the end arms of the shift lever 10.
With the conventional engine starter of the construction as above described, the outer diameter of the pinion 4a which is integrally formed on the outer circumference of the front end of the pinion shifter main body 4b must not be larger than the inner diameter of the bearing 3. This is because, during assembly of the engine starter, the pinion shifter assembly 4, with the output rotary shaft 7 inserted therethrough, is inserted into the housing opening 2 with the bearing 3 fitted therein from the inside (from the left as viewed in FIG. 1) of the housing 1. Therefore, the pinion 4a must pass through the bearing 3, and the outer cylindrical surface of the shifter main body 4b must smoothly fit to the inner diameter of the bearing 3. Therefore, if it is necessary to increase the number of teeth or the outer diameter of the pinion 4a, the entire pinion shifter assembly 4 must be replaced with another pinion shifter 4 having an increased outer diameter of the support surface. This causes the overall dimensions and weight of the engine starter to be disadvantageously increased.